This invention relates generally to detergent compositions, cleaning compositions, and structured surfactant systems having enhanced detergency and cleaning capabilities. It relates more particularly to detergent and cleaning compositions containing the 2-phenyl isomer of linear alkylbenzene sulfonates in concentrations higher than were previously available in the prior art, owing to the discovery of the revolutionary catalyst and process for producing such isomers in high concentration, as detailed herein.
Chemical compounds useful for removing grease, oils, dirt and other foreign matter from various surfaces and objects have been known for some time, including the simple soaps which are manufactured by the saponification of oils (including animal fats and vegetable oils). Saponification is essentially a process whereby aqueous alkali metal hydroxide is mixed with an ester (such as an animal fat or vegetable oil) to cause de-esterification of the ester with the formation of the alkali salt(s) of the carboxylic acid(s) from which the ester was derived, which salt(s) are typically very soluble in aqueous media. Importantly, the anion portions of such alkali salts of the carboxylic acid(s) include as part of their molecular structure a hydrophilic portion, i.e., the carboxylate function, which is highly attracted to water molecules. Such salts also include a hydrophobic portion as part of their molecular structure, which is typically a hydrocarbon-based portion containing between about 12 and 22 carbon atoms per molecule. Such salts are commonly referred to by those skilled in the art as “salts of fatty acids”, and are often commonly referred to by laypersons as “soap”. Aqueous solutions of salts of fatty acids are very effective at causing grease, oils, and other normally water-insoluble materials to become soluble and thus capable of being rinsed away, thus leaving behind a clean substrate which may typically comprise a tabletop, countertop, article of glassware or dinnerware, flatware, clothing, architecture, motor vehicle, human skin, human hair, etc.
While the industries for the production of such soaps from fats and oils are now well-established, saponification chemists and other workers have continuously sought improved chemistry for rendering materials which are not normally soluble in aqueous media to become soluble therein. Towards this end, a wide variety of materials have been identified by those skilled in the art, with the common denominator of such materials being that the materials all contain a hydrophobic portion and a hydrophilic portion in their molecular structures.
One family of materials that have been identified as suitable soap substitutes are the linear alkylbenzene sulfonates (“LAB sulfonates”). The LAB sulfonates in general are exemplified as comprising a benzene ring structure having a hydrocarbyl substituent (or “alkyl substituent”) and a sulfonate group bonded to the ring in the para position with respect to one another. The length of the hydrocarbon chain of the alkyl substituent on the ring is selected to provide a high level of detergency characteristics while the linearity of the hydrocarbon chain enhances the biodegradability characteristics of the LAB sulfonate. The hydrocarbyl substituent may typically contain 6, 7, 8, 9, 10, 11, 12, 13, 14 or 15 carbon atoms (the “detergent range”) in a substantially linear arrangement, and may be attached to the benzene ring through a conventional Friedel-Crafts alkylation process using a corresponding olefin and employing a Lewis acid catalyst such as aluminum chloride and conditions known to those skilled in the art as useful for such alkylations. Various alkylation processes useful for production of alkylbenzenes are described in U.S. Pat. Nos. 3,342,888; 3,478,118; 3,631,123; 4,072,730; 4,301,316; 4,301,317; 4,467,128; 4,503,277; 4,783,567; 4,891,466; 4,962,256; 5,012,021; 5,196,574; 5,302,732; 5,344,997; and 5,574,198, as well as European patent application 353813 and Russian patent 739,046, the entire contents of which are incorporated herein by reference thereto.
Once a hydrocarbyl radical has been appended to a benzene ring in accordance with the foregoing, the resulting linear alkylbenzene must subsequently be sulfonated in order to produce a finished detergent material that is capable of solubilizing grease, oils, dirt, and the like from various substrates, such as dishes, motorized vehicles, hard surfaces, architecture, and fabrics, to name but a few. Sulfonation is a known chemical process whose reactants and conditions are known to those skilled in the chemical arts. Through the process of sulfonation, a sulfonate group is caused to become chemically bonded to a carbon atom in the benzene ring structure of the linear alkylbenzene, thus providing the molecule as a whole with a hydrophilic sulfonate group in addition to the hydrophobic hydrocarbyl portion.
It is known that during the course of mono-alkylation of the benzene ring to introduce a hydrocarbon tail into the molecular structure, several structural isomers are possible in which the benzene ring is attached to various points along the hydrocarbon chain used. It is generally believed that steric effects of the mono-olefin employed play a role in the distribution of isomers in the mono-alkylated product, in addition to the catalyst characteristics and reaction conditions. Thus, it is possible for a single benzene ring to become attached to, say, the 2, 3, 4, or 5 positions in a 10 carbon atom linear mono-olefin, with a different alkylbenzene isomer being produced in each such case. Sulfonation of such different materials results in as many different alkylbenzene sulfonates, each of which have different solubilization capabilities with respect to various oils, grease, and dirt, etc.
The sulfonates of the 2-phenyl alkyl isomers are regarded by those skilled in the art as being very highly desirable materials, as sulfonated linear alkylbenzene detergent materials made from sulfonation of the 2-phenyl alkyl materials have superior cleaning and detergency powers with respect to the sulfonation products of other isomers produced during the alkylation. The general structure of the most desired 2-phenyl alkyl isomer products may be defined as: which in a preferred embodiment has n equal to any integer selected from the group consisting of: 5, 6, 7, 8, 9, 10, 11, and 12. Since the Friedel-Crafts type alkylation employed to produce 2-phenyl alkyl isomers according to the invention may often utilize a mixture of olefins in the detergent range (C8 to C15), a distribution of various alkylbenzenes results from such alkylation. The present invention is therefore in one broad respect concerned with the use of sulfonated 2-phenyl alkylbenzenes derived from the alkylation of benzene, preferably using α-mono olefins having a carbon number distribution in the detergent range, in detergent formulations.
As mentioned above, a 2-phenyl alkylbenzene is but one possible structural isomer resulting from the alkylation of benzene with an olefin, and a mixture of 2-phenyl alkylbenzenes results from the alkylation of benzene using as reactants a feed which includes a mixture of olefins in the detergent range. This may be due to resonance stabilization which permits effective movement of the double bond in an activated olefin/Lewis acid complex. Generally speaking, the collection of all isomeric products produced from the alkylation of benzene with a mixture of olefins in the detergent range is commonly referred to by those of ordinary skill in the art as “linear alkylbenzenes”, or “LAB's”. Frequently, those skilled in the art use “linear alkylbenzenes” or “LAB's” interchangeably with their sulfonates. It is common for people to say LAB's when they are actually referring to sulfonated LAB's useful as detergents.
Typically, LAB's are manufactured commercially using classic Friedal-Crafts chemistry, employing catalysts such as aluminum chloride, or using strong acid catalysts such as hydrogen fluoride, for example, to alkylate benzene with olefins. While such methods produce high conversions, the selectivity to the 2-phenyl isomer in such reactions as known in the prior art is low, generally being about 30% or less. LAB's with a high percentage of the 2-phenyl isomer are highly desired because such compounds when sulfonated have long “tails” which provide enhanced solubility and detergent properties.
Liquid detergent compositions containing a bleach component and which are useful in cleaning substrates such as laundry, hard surfaces, carpet spot removers, tub and tile cleaners, and other substrates have been provided by workers in the surfactants field in two general varieties. The first general variety involves the use of hypochlorite bleaches, such as calcium and sodium hypochlorite, often in combination with amine oxides and one or more ether sulfates. Formulations containing such a bleaching agent are not color stable and can only be used on substrates which are free from dyestuffs, such as white clothing.
The second general variety involves the use of hydrogen peroxide as a bleaching agent. However, detergents containing hydrogen peroxide based bleaching agents must be formulated at low pH in order to avoid conditions under which the peroxide spontaneously decomposes. Owing to a lack of control of the stability of hydrogen peroxide, it is often added as a separate component along with various other detergents.
In relatively recent practice, peroxygen bleaches have come into popular usage as components in powdered detergent formulations for the consumer laundry market, with sodium percarbonate and sodium perborate being those most commonly employed active peroxygen bleaches. Detergent formulations which contain these bleaches have the advantage over hypochlorite bleaches in that they are color stable, i.e., they do not cause degradation of the color qualities of colored fabrics when employed as a laundry detergent. However, they also have the drawback in that they cannot be used in liquid detergents which contain water, due to their reactivity towards water, which would otherwise lead to stability problems during handling and storage. Thus, a stable liquid detergent formulated to contain peroxygen bleaches such as perborates and percarbonates are highly desirable, in principle.
Several workers have attempted to provide detergent systems which employ substantially anhydrous structured surfactants, in order to produce systems which are capable of suspending solid particles of bleaching materials within their bulk; however, the stability of the system overall has in every case thus far been an insurmountable problem, particularly at relatively elevated temperatures normally encountered during handling and storage of detergents. In these previous attempts, anionic surfactants are dissolved in a liquid nonionic surfactant, and subsequently cross-linked with divalent cations, such as calcium or magnesium, (or alternatively with a diamine, such as ethylene diamine). Unfortunately, for laundry applications, the presence of the hardness cations Ca++ or Mg++ decreases detergency effectiveness. Additionally, diamines such as ethylene diamine are known human skin sensitization agents, and any residual quantities of diamines on fabric are likely to lead to conditions of contact dermatitis. As an added complication, such systems show a phase separation upon standing and the water of neutralization tends to cause the bleaching agent to decompose.
Thus, if a structured system containing suspended bleach particles could be devised, wherein the system did not suffer the aforesaid drawbacks, such a system would be welcomed by industry. The present invention provides such systems. Advantages of compositions according to the present invention include the ability to suspend peroxygen bleach in a liquid system and still retain the bleaching action after prolonged storage. It is likely that other moisture sensitive or incompatible materials besides bleaches could also be suspended using a system according to the invention, including enzymes, fabric softeners, peracids and the like.